(a) Field of the Invention
The present invention relates to a matrix-type transdermal drug delivery system including capsaicin or a capsaicin derivative as an active component and that is used for treating neuropathy, pain, or inflammation, and a preparation method thereof.
(b) Description of the Related Art
The present invention relates to a matrix-type transdermal drug delivery system including capsaicin or a capsaicin derivative as an active component and that is used for treating neuropathy, pain, or inflammation, and a preparation method thereof. More particularly, the present invention relates to a matrix-type transdermal drug delivery system that is capable of enhancing skin permeability and extending the medical efficacy maintaining time of the capsaicin or the capsaicin derivative, that is, the active component. The present invention also relates to a preparing method of the matrix-type transdermal drug delivery system that is capable of preparing the matrix-type transdermal drug delivery system more easily in a short time.
Capsaicin is the active component of hot peppers that causes a spicy taste, and it is represented by the chemical name N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-6-enamide). It is known that the capsaicin stimulates pain neurons of the sensory nerves and causes pain, and releases various mediators of inflammation at the early stage of administration, but its continuous administration incapacitates the neurons and brings an insensible state to other external stimulators as well as to the capsaicin. Such action of the capsaicin is called desensitization.
It is also known that the analgesic effect due to such desensitization is different from the analgesic effect of other anodynes in its functional mechanisms, and the analgesic effect is as strong as morphine. Furthermore, it is known that the capsaicin may be effectively used for treating neuropathy or inflammation. However, the capsaicin shows a stimulation effect at the early stage of oral administration, and it may give rise to hypothermia, contraction of the bronchial tube, increase of gastrointestinal activity, side effects to the cardiovascular system, such as hypotonia, or side effects to the respiratory system.
To inhibit such side effects due to the oral administration of the capsaicin, various studies for formulating the capsaicin into a transdermal medicine have been carried out. Representatively, products that are fabricated as ointments have come on the market, and studies for formulating the same into a transdermal medicine, i.e., a patch, are now under way.
Technologies regarding topical functional medicines, such as ointments, are disclosed in U.S. Pat. Nos. 5,178,879, 5,910,512, 6,348,501, and 6,593,370. Particularly, the technologies disclosed in the patents are mainly related to medical compositions, such as gels, lotions, or ointments, and the medical compositions are directly used on skin without a drug protecting layer that seals the active components. However, when the capsaicin is formulated into an ointment and the like, without the drug protecting layer, its smell stimulates the respiratory system and may cause similar side effects to the case of the oral administration, because the volatility of the capsaicin is relatively high. Furthermore, when the capsaicin is formulated into an ointment and the like, it is required to rub the ointment three or four times or more a day by hand, because the skin permeability of the capsaicin may be reduced and the medical efficacy maintaining time is shortened. Further, the capsaicin remains on the hand, and therefore it may unnecessarily cause stimulation or pain, and it also may cause inconvenience in that clothes are stained by the ointment. Especially, such inconvenience increases because it is required to rub the ointment for a long time for treating pain and the like by using the capsaicin.
In addition, a patch including a drug protecting layer, a polysiloxane-based layer including capsaicin, diethyleneglycol monoethyl ether, ethyl cellulose, and a silicone oil is disclosed in U.S. Publication No. 2004/0202707.
Furthermore, a method of eliminating capsaicin remaining on the skin by using a cleansing gel after using a patch including capsaicin in a large quantity on the skin and removing the patch is disclosed in PCT publication No. WO04/021990. In such method, the capsaicin of a large quantity may stimulate the skin severely, and it is inconvenient in that the skin must be separately cleaned by using a cleansing gel after removing the patch. Furthermore, the medical efficacy maintaining time cannot be increased sufficiently, even though the capsaicin is formulated into the patch.